Polishing apparatus

ABSTRACT

A polishing apparatus is used to polish a workpiece such as a semiconductor wafer. The polishing apparatus includes a polishing table having a polishing surface, a dresser for dressing the polishing surface, a substrate holder for holding and pressing a substrate against the polishing surface to polish the substrate with relative movement between the polishing surface and the substrate. The dresser includes a first dressing member and a second dressing member. The first dressing member has a circular shape having a diameter larger than a diameter of the substrate. The second dressing member is shaped so as to surround the first dressing member. The first dressing member and the second dressing member are operable to come into contact with the polishing surface independently of each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing apparatus for polishing a workpiece, such as a semiconductor wafer (e.g., silicon wafer), and more particularly to a polishing apparatus having a dresser for dressing a polishing surface of a polishing table.

2. Description of the Related Art

With a recent progress in semiconductor devices toward finer structure and higher integration, a distance between interconnects is becoming smaller and smaller. Especially, when forming a circuit pattern by optical lithography with a line width of not more than 0.5 μm, surfaces, on which pattern images are to be focused by a stepper, are required to be flat because depth of focus is small. Thus, in order to achieve flat surfaces, a polishing apparatus has been widely used to polish the surfaces.

This type of polishing apparatus includes a polishing table having a polishing pad attached to an upper surface thereof, and a top ring, serving as a substrate-holding mechanism, for holding a substrate to be polished. The polishing table and the substrate-holding mechanism are independently rotated at different speeds. The substrate is held by the top ring and pressed against a polishing surface of the polishing pad on the polishing table while a polishing liquid is supplied onto the polishing surface, whereby the substrate is polished to have a flat and mirror-finished surface. Some types of polishing apparatuses are designed to press a surface of a substrate with uniform pressure in order to achieve uniform polishing, as disclosed in Japanese laid-open patent publication No. 2004-249452. After polishing, the substrate is released from the top ring and is then transferred to a subsequent process, e.g., cleaning process.

In order to uniformly polish a surface of a substrate, it is necessary to perform conditioning, i.e., dressing, on the polishing surface of the polishing pad on the polishing table. There are two timings for performing dressing: one is dressing during polishing, and another is dressing after polishing, When dressing during polishing, it is important to prevent detachment of diamond particles from a dresser because the detached diamond particles would scratch the surface of the substrate to be polished. When dressing after polishing, a dressing speed is important. Generally, for the purpose of preventing detachment of the diamond particles, a dresser having small diamond particles, which are electrodeposited thereto and have rounded edges, is used, and a low load (i.e., small pressing force) is applied. As a result, the dressing speed is lowered.

Ideal dressing of the polishing surface of the polishing table is to keep the polishing surface in a best condition by dressing it during polishing, and to hold a shape of the polishing surface unchanged even after the polishing surface is scraped off. For example, on one hand, a dresser designed to dress a polishing surface at a low cut rate is suited to the former, and on the other hand, a dresser designed to dress a polishing surface at a high cut rate is suited to the latter. This means that it is difficult to achieve both of these effects with a single dresser.

Further, after replacing the polishing pad with a new one, dressing is typically performed for about 10 minutes, and then dummy polishing is performed using about 25 dummy wafers. This operation is performed in order to bring the polishing pad closer to a ready condition for practical use. However, dummy polishing requires cleaning of the dummy wafers and, as a result, downtime of the apparatus would be increased.

With regard to a removal rate (polishing rate), a state of the dressed polishing surface is important, as described above. In addition, a temperature of the polishing surface during polishing also affects the removal rate. In a polishing process that greatly depends on a temperature, e.g., in a case where the removal rate is lowered as the temperature increases, it is possible to prevent a decrease in removal rate during polishing by preventing an increase in temperature during polishing. Further, an increase in temperature of the polishing surface results in a decrease in hardness of the resin polishing pad forming the polishing surface, thus adversely affecting flattening capability.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above drawbacks. It is therefore an object of the present invention to provide a polishing apparatus which can maintain a polishing surface of a polishing table in suitable conditions during polishing, can hold a shape of the polishing surface unchanged even after the polishing surface is scraped off, and can polish a substrate at a high removal rate while suppressing an increase in temperature of the polishing surface.

Further, another object of the present invention is to provide a polishing apparatus which can shorten downtime of the apparatus required for bringing a new polishing pad closer to a ready condition for practical use after placement of a polishing pad.

In order to solve the above drawbacks, one aspect of the present invention provides a polishing apparatus comprising a polishing table having a polishing surface, a dresser for dressing the polishing surface, a substrate holder for holding and pressing a substrate against the polishing surface to polish the substrate with relative movement between the polishing surface and the substrate. The dresser includes a first dressing member and a second dressing member. The first dressing member has a circular or disk shape having a diameter larger than a diameter of the substrate. The second dressing member is shaped so as to surround the first dressing member. The first dressing member and the second dressing member are operable to come into contact with the polishing surface independently of each other.

According to the present invention described above, the first dressing member and the second dressing member can independently dress the polishing surface at different timings. The first dressing member can have a dressing surface with small diamond particles fixed thereto so that a cut rate is low. The second dressing member can have a dressing surface with large diamond particles fixed thereto so that a cut rate is high. In this case, the first dressing member dresses the polishing surface during polishing of the substrate, and the second dressing member dresses the polishing surface after polishing of the substrate. With this operation, the substrate is polished immediately after dressing, i.e., conditioning, by a dressed zone of the polishing surface which is slightly larger than a substrate-contacting zone. Accordingly, the substrate can be polished at a high removal rate. Further, after polishing, the second dressing member can quickly dress the polishing surface in its entirety at a high cut rate. In this manner, the first and second dressing members can be separately used.

In a preferred aspect of the present invention, the first dressing member and the second dressing member have rotating shafts, respectively. The rotating shafts of the first dressing member and the second dressing member are concentrically arranged and are rotatable independently of each other.

According to the present invention described above, the first dressing member and the second dressing member can be arranged along a vertical direction. Therefore, an arrangement space on the polishing surface can be small, and the dresser can be compact.

In a preferred aspect of the present invention, a cut rate of the polishing surface by the first dressing member is lower than that by the second dressing member.

According to the present invention described above, the substrate can be polished by the polishing surface immediately after the first dressing member dresses the polishing surface at a low cut rate, and therefore efficient polishing can be performed. Further, after polishing, the second dressing member can quickly dress the polishing surface in its entirety at a high cut rate.

In a preferred aspect of the present invention, the first dressing member is operable to dress the polishing surface of the polishing table during polishing of the substrate.

According to the present invention described above, the substrate can be polished by the polishing surface immediately after dressing. As a result, polishing can be performed at a high removal rate.

In a preferred aspect of the present invention, the first dressing member and the second dressing member are operable to control a pressing force applied to the polishing surface of the polishing table independently of each other.

According to the present invention described above, the first dressing member and the second dressing member can dress the polishing surface at different cut rates. For example, during polishing, the first dressing member can dress the polishing surface with a small pressing force, and after polishing, the second dressing member can quickly dress the polishing surface in its entirety with a large pressing force.

In a preferred aspect of the present invention, the first dressing member includes a fluid passage through which a cooling or heating medium circulates.

According to the present invention described above, the polishing surface can be dressed while cooled or heated by the medium. As a result, highly flat dressing can be achieved, and the substrate can be polished at a high removal rate.

In a preferred aspect of the present invention, the polishing apparatus further comprises a temperature controller for adjusting and controlling a temperature of the cooling or heating medium circulating the fluid passage.

According to the present invention described above, the dressed polishing surface can be maintained at an appropriate temperature. As a result, highly flat dressing can be achieved, and the substrate can be polished at a high removal rate.

Another aspect of the present invention provides a polishing apparatus comprising a polishing table having a polishing surface, a dresser for dressing the polishing surface, a substrate holder for holding and pressing a substrate against the polishing surface to polish the substrate with relative movement between the polishing surface and the substrate. The dresser includes a circular holding member for holding a circular dummy substrate, and a dressing member arranged around the circular holding member.

According to the present invention described above, the polishing surface can be dressed while the dummy substrate is pressed against the polishing surface. As a result, downtime of the apparatus can be shortened.

In a preferred aspect of the present invention, the circular holding member and the dressing member have rotating shafts, respectively, and the rotating shafts are concentrically arranged and are rotatable independently of each other.

According to the present invention described above, the circular holding member and the dressing member can be arranged along a vertical direction. Therefore, an arrangement space on the polishing surface can be small, and the dresser can be compact.

In a preferred aspect of the present invention, the circular holding member includes therein a fluid passage through which a cooling or heating medium circulates.

According to the present invention described above, heat of the dummy substrate is absorbed, and hence an increase in temperature thereof can be suppressed.

In a preferred aspect of the present invention, the circular holding member is operable to press the dummy substrate against the polishing surface of the polishing table during polishing of the substrate.

According to the present invention described above, the polishing surface can be maintained at an appropriate temperature. As a result, the substrate can be polished at a high removal rate.

In a preferred aspect of the present invention, the polishing surface of the polishing table comprises a surface of a polishing pad attached to an upper surface of the polishing table. The polishing apparatus is operable such that, after the polishing pad is replaced with a new polishing pad, the dummy substrate held by the circular holding member and the dressing member are pressed against a polishing surface of the new polishing pad to thereby break in the polishing surface of the new polishing pad.

According to the present invention described above, the polishing surface of the polishing pad can be in a ready condition for practical use in a short period of time.

In a preferred aspect of the present invention, a SiC wafer is used as the dummy substrate.

According to the present invention described above, the SiC water can be used for a long time as the dummy substrate.

In a preferred aspect of the present invention, the circular holding member is operable to press the dummy substrate against the polishing surface of the polishing table during polishing of the substrate.

According to the present invention described above, heat due to friction between the substrate and the polishing surface can be absorbed, and hence polishing efficiency can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a structural example of a polishing apparatus according to the present invention;

FIGS. 2A through 2C are views showing a structural example of a first dressing member of the polishing apparatus according to the present invention, FIG. 2A being a plan view, FIG. 2B being a cross-sectional view taken along line A-A shown in FIG. 2A, FIG. 2C being an enlarged cross-sectional view showing a part of a dressing surface;

FIGS. 3A and 3B are views showing a structure of a second dressing member of the polishing apparatus according to the present invention, FIG. 3A being a cross-sectional view of the second dressing member, FIG. 3B being an enlarged cross-sectional view showing a part of a dressing surface;

FIGS. 4A and 4B are views showing a dresser of the polishing apparatus according to the present invention, FIG. 4A being a cross-sectional view illustrating a state in which the first dressing member performs dressing, FIG. 4B being a cross-sectional view illustrating a state in which the second dressing member performs dressing;

FIG. 5 is a view showing an arrangement of a substrate and the first dressing member on an upper surface of a polishing pad during polishing according to the present invention;

FIG. 6 is a view showing an arrangement of the substrate and the second dressing member on the upper surface of the polishing pad after polishing according to the present invention;

FIGS. 7A and 7B are views showing an example of a dresser of the polishing apparatus according to the present invention, FIG. 7A being a cross-sectional view illustrating a state in which a circular holding member protrudes from the dressing member, FIG. 7B being a cross-sectional view illustrating a state in which the circular holding member is accommodated in a recessed portion of the dressing member;

FIG. 8 is a cross-sectional view illustrating an operating state of the dresser when starting up a polishing pad of the polishing apparatus according to the present invention;

FIG. 9 is a cross-sectional view illustrating an operating state of the dresser when breaking in a polishing surface of the polishing pad of the polishing apparatus according to the present invention;

FIG. 10 is a cross-sectional view illustrating an operating state of the dresser during polishing according to the present invention; and

FIG. 11 is a plan view showing the polishing surface of the polishing apparatus according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a structural example of a polishing apparatus according to the present invention. In FIG. 1, a reference numeral 10 represents a polishing table. A polishing pad 11 is attached to an upper surface of the polishing table 10. The polishing table 10 is rotated by a non-illustrated rotating mechanism in a direction indicated by arrow A.

A reference numeral 12 represents a substrate holder (top ring). This substrate holder 12 comprises a circular substrate-holding member 13 for attracting and holding a substrate (e.g., a silicon wafer) W to be polished. The substrate-holding member 13 has an attraction surface configured to attract the substrate W thereto, and this attraction surface has a plurality of openings 13 a communicating with a space chamber 14 formed in the substrate-holding member 13. The space chamber 14 is coupled to a vacuum source 15 via a valve 16, so that the substrate W is held on the attraction surface by opening the valve 16 and is released from the attraction surface by closing the valve 16.

The substrate holder 12 is coupled to a lower edge portion of a rotating shaft 17 via a universal coupling 18, so that rotation of the rotating shaft 17 in a direction indicated by arrow B rotates the substrate holder 12 in the same direction. A reference numeral 19 represents a head member for rotatably supporting the rotating shaft 17. This head member 19 is fixed to a support shaft 20. A reference numeral 21 represents an air cylinder mounted on the head member 19. This air cylinder 21 is operable to elevate and lower the substrate holder 12 via a piston member 22 and the rotating shaft 17, and to bring the substrate W into contact with a polishing surface of the polishing pad 11 at a predetermined pressing force (load). A reference numeral 23 represents a bearing.

A reference numeral 24 represents a driving motor mounted on the head member 19. A timing pulley 25 is coupled to a rotating shaft of the driving motor 24. A timing belt 27 rides on the timing pulley 25 and a timing pulley 26 fixed to a circumferential surface of the rotating shaft 17. By energizing the driving motor 24, the substrate holder 12 is rotated in the direction B via the timing pulley 25, the timing belt 27, the timing pulley 26, and the rotating shaft 17. Rotation of the polishing table 10 in the direction A and rotation of the substrate holder 12 in the direction B provide relative movement between the substrate W and the polishing pad 11 to thereby polish the substrate W. A reference numeral 28 represents a guide ring for preventing the substrate W from being spun off from the substrate-holding member 13.

The support shaft 20 is rotated through a certain angle by a non-illustrated rotating mechanism, so that the head member 19 is swung by rotation of the support shaft 20 to thereby allow the substrate holder 12 to move between a predetermined substrate-transfer position where the substrate W is transferred and a polishing position on the polishing pad 11. The substrate holder 12 attracts and holds the substrate W at the substrate-transfer position, and is moved by swinging motion of the head member 19 to the polishing position. Then, the substrate holder 12 is moved downward to bring the substrate W into contact with the upper surface of the polishing pad 11 at a predetermined pressing force. The substrate holder 12 and the polishing table 10 are rotated to provide relative movement between the substrate W and the polishing pad 11 to thereby polish the substrate W. Thereafter, the substrate holder 12 is moved to the substrate-transfer position, and releases the polished substrate W. Such steps are repeated, whereby substrates W are polished.

A reference numeral 30 represents a dresser for dressing, i.e., conditioning, the polishing surface of the polishing pad 11 on the polishing table 10. This dresser 30 comprises a first dressing member 31 and a second dressing member 32. The first dressing member 31 has a circular or disk shape with a larger diameter than that of the substrate W, and has a lower surface serving as a dressing surface, which will be discussed later, with a large number of diamond particles fixed thereto for dressing the polishing surface of the polishing pad 11. The second dressing member 32 has a disk-shape with a larger diameter than that of the first dressing member 31. The second dressing member 32 has a recessed portion 32 a at a central portion of a lower surface thereof, and the first dressing member 31 is accommodated in this recessed portion 32 a. A lower surface of the second dressing member 32 provides an annular belt-shaped surface serving as a dressing surface, which will be discussed later, with a large number of diamond particles fixed thereto for dressing the polishing surface of the polishing pad 11.

The first dressing member 31 is fixed to a lower end of a rotating shaft 33, and the second dressing member 32 is fixed to a lower end of a rotating shaft 34. The rotating shaft 33 extends through the rotating shaft 34, and is supported by bearings 35 and 36 that allow the rotating shaft 33 to be free to rotate in the rotating shaft 34. The rotating shaft 33 is rotatably supported by a head member 37, and the rotating shaft 34 is rotatably supported by a head member 38. A reference numeral 39 represents an air cylinder mounted on the head member 37. This air cylinder 39 is operable to elevate and lower the first dressing member 31 via a piston member 40 and the rotating shaft 33, and to bring the first dressing member 31 into contact with the polishing surface of the polishing pad 11 at a predetermined pressing force (load). A reference numeral 41 represents a bearing. A reference numeral 42 represents an air cylinder mounted on the head member 38. This air cylinder 42 is operable to elevate and lower the second dressing member 32 via a piston member 43 and the rotating shaft 34, and to bring the second dressing member 32 into contact with the polishing surface of the polishing pad 11 at a predetermined pressing force (load). A reference numeral 44 represents a bearing.

A reference numeral 45 represents a driving motor mounted on the head member 37. This driving motor 45 has a rotating shaft with a timing pulley 47 fixed thereto. A timing belt 49 rides on the timing pulley 47 and a timing pulley 48 fixed to a circumferential surface of the rotating shaft 33. By energizing the driving motor 45, the first dressing member 31 is rotated in a direction indicated by arrow C via the timing pulley 47, the timing belt 49, the timing pulley 48, and the rotating shaft 33. A reference numeral 50 represents a driving motor mounted on the head member 38. This driving motor 50 has a rotating shaft with a timing pulley 51 fixed thereto. A timing belt 53 rides on the timing pulley 51 and a timing pulley 52 fixed to a circumferential surface of the rotating shaft 34. By energizing the driving motor 50, the second dressing member 32 is rotated in a direction indicated by arrow D via the timing pulley 51, the timing belt 53, the timing pulley 52, and the rotating shaft 34.

As described above, the first dressing member 31 and the second dressing member 32 have the rotating shaft 33 and the rotating shaft 34, respectively, which have the same axis (they are concentrically arranged) and are rotated independently of each other in the directions indicated by arrows C and D. Further, the first dressing member 31 and the second dressing member 32 are elevated and lowered independently of each other by the air cylinder 39 and the air cylinder 42, respectively, and are thus pressed against the polishing surface at desired pressing forces (loads). The head member 37 and the head member 38 have edge portions, respectively, which are fixed to a support shaft 54. This support shaft 54 is rotated through a certain angle by a non-illustrated driving mechanism, so that the head members 37 and 38 are swung by rotation of the support shaft 54 to thereby allow the first dressing member 31 and the second dressing member 32 to move between predetermined waiting positions and dressing positions on the polishing pad 11.

As shown in FIGS. 2A through 2C, the first dressing member 31 comprises a disk-shaped body 31 a having a lower surface. A large number of diamond particles 3 b are fixed to the lower surface via a fixing layer (an electrodeposited layer) 31 c formed on the lower surface to thereby form the dressing surface. A fluid passage 31 d is formed in the disk-shaped body 31 a so that a cooling medium circulates through the fluid passage 31 d. The rotating shaft 33 has therein a fluid-introduction passage 33 a through which the cooling medium is introduced into the fluid passage 31 d, and further has therein a fluid-discharge passage 33 b through which the cooling medium flows out from the fluid passage 31 d. The cooling medium 100 (see FIG. 1), which has been introduced into the fluid-introduction passage 33 a, flows through the fluid passage 31 d in the disk-shaped body 31 a to thereby cool the disk-shaped body 31 a, and flows out from the fluid passage 31 d through the fluid-discharge passage 33 b. Instead of the cooling medium for cooling the body 31 a, a heating medium for heating the body 31 a may be introduced into the fluid passage 31 d. FIG. 2A is a plan view showing the first dressing member 31, FIG. 2B is a cross-sectional view taken along line A-A of FIG. 2A, and FIG. 2C is an enlarged cross-sectional view showing a part of the dressing surface.

The second dressing member 32 comprises a disk-shaped body 32 b having the recessed portion 32 a at the center of the lower surface thereof for accommodating the first dressing member 31. A large number of diamond particles 32 c are fixed to the lower surface via a fixing layer (an electrodeposited layer) 32 d formed around the recessed portion 32 a to thereby form the dressing surface of an annular belt shape. A through-hole 34 a is formed in the rotating shaft 34, and the rotating shaft 33 of the first dressing member 31 extends through the through-hole 34 a. FIG. 3A is a cross-sectional view showing the second dressing member 32, and FIG. 3B is an enlarged cross-sectional view showing a part of the dressing surface.

The diameters of the diamond particles 31 b fixed to the lower surface of the first dressing member 31 are smaller than the diameters of the diamond particles 32 c fixed to the lower surface of the second dressing member 32. Further, the diamond particles 31 b have more rounded shapes than the diamond particles 32 c. As shown in FIG. 4A, the first dressing member 31, rotating in the direction C, is pressed against the upper surface of the polishing pad 11 moved by the polishing table 10 in the direction A. Similarly, as shown in FIG. 4B, the second dressing member 32, rotating in the direction D, is pressed against the upper surface of the polishing pad 11 moved by the polishing table 10 in the direction A. Because the diamond particles 31 b have smaller diameters and more rounded shapes than those of the diamond particles 32 c, a cut rate of the polishing pad 11 by the first dressing member 31 is lower than that by the second dressing member 32. FIGS. 4A and 4B are views showing the dresser 30 of the polishing apparatus according to the present invention. More specifically, FIG. 4A is a cross-sectional view illustrating a state in which the first dressing member 31 performs dressing (conditioning), and FIG. 4B is a cross-sectional view illustrating a state in which the second dressing member 32 performs dressing (conditioning).

In the above polishing apparatus, the support shaft 54 is rotated to swing the head member 37 and the head member 38 to move the first dressing member 31 and the second dressing member 32 from the waiting positions to the dressing positions on the polishing surface of the polishing pad 11, as shown in FIG. 1. In this state, the air cylinder 39 moves the first dressing member 31 downward to press the lower surface of the first dressing member 31, rotating in the direction C, against the polishing surface of the polishing pad 11, rotating in the direction A, at a predetermined pressing force to thereby dress the polishing surface, as shown in FIG. 4A. On the other hand, in FIG. 4B, the first dressing member 31 is accommodated in the recessed portion 32 a of the second dressing member 32, and the air cylinder 41 moves the second dressing member 32 downward to press the lower surface of the second dressing member 32, rotating in the direction D, against the polishing surface of the polishing pad 11, rotating in the direction A, at a predetermined pressing force to thereby dress the polishing surface.

As described above, there are two timings for dressing of the polishing surface of the polishing pad 11: one is dressing during polishing of the substrate W, and another is dressing after polishing. FIG. 4A shows dressing during polishing of the substrate W, and FIG. 4B shows dressing after polishing. Because the diameter of the first dressing member 31 is larger than the diameter of the substrate W, when dressing in a manner shown in FIG. 4A, a positional relationship on the polishing surface of the polishing pad 11 between the first dressing member 31 and the substrate W is such that the substrate W is positioned within a dressing zone 101 where dressing (conditioning) has been performed by the first dressing member 31, as shown in FIG. 5. Further, because the diameter of the second dressing member 32 is larger than the diameter of the first dressing member 31, the second dressing member 32 can dress the polishing surface in its entirety of the polishing pad 11 in a short period of time after polishing of the substrate W, as shown in FIG. 6.

Because the rotating shaft 33 of the first dressing member 31 and the rotating shaft 34 of the second dressing member 32 are concentrically arranged, and are moved up and down and rotated independently of each other as described above, the first dressing member 31 and the second dressing member 32 can be arranged along a vertical direction. Accordingly, the dresser 30 can be compact.

When performing dressing while polishing the substrate W as shown in FIGS. 4A and 5, the substrate W is polished by the polishing surface immediately after dressing. In addition, the first dressing member 31 is cooled by the cooling medium 100 flowing through the fluid passage 31 d in the disk-shaped body 31 a, so that heat due to friction of the polishing surface and dressing is absorbed. As a result, the polishing surface can be maintained at an appropriate temperature, and the substrate W can thus be polished at a high removal rate. While dressing the polishing surface during polishing of the substrate W, the first dressing member 31 applies a smaller pressing force to the polishing surface than that of the second dressing member 32 applied after polishing. Therefore, heat value is low and the diamond particles are not detached from the dressing surface. When performing dressing after polishing of the substrate W as shown in FIGS. 4B and 6, the dressing surface of the second dressing member 32 is pressed against the polishing surface of the polishing pad 11 at a large pressing force to thereby dress the polishing surface at a high cut rate. Accordingly, the polishing surface of the polishing pad 11 can be rapidly and uniformly dressed.

Although not shown in the drawings, a temperature controller may be provided for adjusting and controlling a temperature of the cooling medium. In this case, the temperature controller can adjust and control the temperature of the cooling medium flowing through the fluid-discharge passage 33 b after the cooling medium has flowed through the fluid passage 31 d to cool or heat the first dressing member 31. After the temperature is adjusted, the cooling medium can be returned to the fluid passage 31 d through the fluid-introduction passage 33 a. With this structure, the polishing surface of the polishing pad 11 can be maintained at a predetermined temperature, and hence the substrate W can be polished at a high constant removal rate.

FIGS. 7A and 7B are views showing another example of the dresser 30 of the polishing apparatus according to the present invention. This dresser 30 comprises a circular holding member 60 for attracting and holding a circular dummy substrate DW, and a dressing member 61 disposed around the circular holding member 60. The circular holding member 60 has an attraction surface configured to attract the dummy substrate DW thereto, and this attraction surface has a plurality of openings 60 a communicating with a space chamber 62 formed in the circular holding member 60. The space chamber 62 is coupled to a vacuum source 64 via a vacuum passage 33 c and a valve 63 provided in rotating shaft 33. The circular holding member 60 is fixed to the rotating shaft 33. By opening the valve 63 so as to communicate the vacuum source 64 with the space chamber 62, the dummy substrate DW is attracted to and held on the attraction surface. The dummy substrate DW is released from the attraction surface by closing the valve 63 so as to isolate the space chamber 62 from the vacuum source 64. FIG. 7A is a cross-sectional view illustrating a state in which the circular holding member 60 protrudes from the dressing member 61, and FIG. 7B is a cross-sectional view illustrating a state in which the circular holding member 60 is accommodated in a recessed portion 61 a of the dressing member 61.

A diameter of the circular holding member 60 is larger than that of the substrate W. As with the first dressing member 31, the circular holding member 60 has therein a fluid passage 60 b for circulating a cooling medium. The rotating shaft 33 has therein fluid-introduction passage 33 a through which the cooling medium is introduced into the fluid passage 60 b, and further has fluid-discharge passage 33 b through which the cooling medium flows out from the fluid passage 60 b. The cooling medium 100 (see FIG. 1), which has been introduced into the fluid-introduction passage 33 a, flows through the fluid passage 60 b to thereby cool the circular holding member 60, and flows out through the fluid-discharge passage 33 b. Although not shown in the drawings, a temperature controller may be provided for adjusting and controlling a temperature of the cooling medium circulating through the fluid passage 60 b in the circular holding member 60, as with the first dressing member 31, so that the circular holding member 60 can be maintained at a predetermined temperature.

The dressing member 61 has the same structure as that of the second dressing member 32 shown in FIGS. 3A and 3B. More specifically, the dressing member 61 has the recessed portion 61 a at a center of a lower surface thereof for accommodating the circular holding member 60. The dressing member 61 has an annular belt-shaped surface at a lower end thereof, and a large number of diamond particles are fixed to the annular belt-shaped surface for dressing the polishing surface of the polishing pad 11. Vertical movement and rotating motion of the circular holding member 60 are performed in the same manner as those of the first dressing member 31, and will not be described. Further, vertical movement and rotating motion of the dressing member 61 are performed in the same manner as those of the second dressing member 32, and will not be described. As with the rotating shaft 33 of the first dressing member 31 and the rotating shaft 34 of the second dressing member 32, the rotating shaft 33 of the circular holding member 60 and the rotating shaft 34 of the dressing member 61 have the same axis (i.e., they are concentrically arranged), and are moved up and down and rotated independently of each other.

After the polishing pad 11 on the polishing table 10 is replaced with a new one, starting up of the new polishing pad is performed. Specifically, as shown in FIG. 8, the dressing member 61 is rotated in the direction D, and the lower surface thereof, i.e., the dressing surface with a large number of diamond particles fixed thereto, is pressed against a polishing surface (upper surface) of the new polishing pad 11 moving in the direction A with rotation of the polishing table 10. Simultaneously, a dummy semiconductor substrate (e.g., silicon wafer) DW is attracted to the attraction surface of the circular holding member 60, and is pressed against the polishing surface of the polishing pad 11 at a predetermined pressing force. With this operation, downtime of the polishing apparatus can be shortened. The circular holding member 60 is cooled by the cooling medium flowing through the fluid passages 60 b. Therefore, heat due to friction of the dummy semiconductor substrate DW is absorbed, and hence an increase in temperature is suppressed. As the dummy semiconductor substrate DW, a SiC wafer having a higher wear resistance than the silicon wafer may be used.

After the polishing pad 11 on the polishing table 10 is started up, a dummy semiconductor substrate (e.g., silicon wafer) DW is held by the circular holding member 60 of the dresser 30, and is rotated in the direction C, as shown in FIG. 9. Then, the dummy semiconductor substrate DW is pressed at a predetermined pressing force (load) against the polishing surface (upper surface) of the polishing pad 11 moving in the direction A with rotation of the polishing table 10, whereby break-in is performed. During this operation, the cooling medium circulates through the fluid passage 60 b of the circular holding member 60. As a result, frictional heat of the dummy semiconductor substrate DW is absorbed by the cooling medium, and hence an increase in temperature of the dummy semiconductor substrate DW can be suppressed.

Further, while polishing the substrate W held by the substrate holder 12 (see FIG. 1), the lower surface of the circular holding member 60, rotating in the direction C, is pressed against the polishing surface of the polishing pad 11 moving in the direction A with rotation of the polishing table 10, as shown in FIG. 10. In this case, the openings 60 d for attracting the dummy semiconductor substrate DW and the space chamber 62 may not be formed, although shown in FIG. 10. The cooling medium circulates through the fluid passage 60 b to cool the circular holding member 60, so that heat of the polishing surface of the polishing pad 11, which is held in contact with the circular holding member 60, is absorbed by the cooling medium. More specifically, as shown in FIG. 11, an increase in temperature of a zone 102 contacting the circular holding member 60 is suppressed, and hence a temperature suitable for polishing can be maintained. As a result, the substrate W can be polished at a high removal rate.

Furthermore, while polishing the substrate W, the dummy semiconductor substrate DW, held by the circular holding member 60, is kept in contact with the upper surface of the polishing pad 11 as shown in FIG. 9, so that the upper surface (polishing surface) of the polishing pad 11 is cooled by the cooling medium via the dummy semiconductor substrate DW. Accordingly, as with the above case, the substrate W can be polished at a high removal rate.

Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of claims for patent, and the scope of the technical concept described in the specification and drawings. 

1. A polishing apparatus, comprising: a polishing table having a polishing surface; a dresser for dressing said polishing surface; a substrate holder for holding and pressing a substrate against said polishing surface to polish the substrate with relative movement between said polishing surface and the substrate, wherein said dresser includes a first dressing member and a second dressing member, said first dressing member has a circular or disk shape having a diameter larger than a diameter of the substrate, said second dressing member is shaped so as to surround said first dressing member, and said first dressing member and said second dressing member are operable to come into contact with said polishing surface independently of each other.
 2. The polishing apparatus according to claim 1, wherein: said first dressing member and said second dressing member have rotating shafts, respectively; said rotating shafts of said first dressing member and said second dressing member are concentrically arranged and are rotatable independently of each other.
 3. The polishing apparatus according to claim 1, wherein a cut rate of said polishing surface by said first dressing member is lower than that by said second dressing member.
 4. The polishing apparatus according to claim 1, wherein said first dressing member is operable to dress said polishing surface of said polishing table during polishing of the substrate.
 5. The polishing apparatus according to claim 1, wherein said first dressing member and said second dressing member are operable to control a pressing force applied to said polishing surface of said polishing table independently of each other.
 6. The polishing apparatus according to claim 1, wherein said first dressing member includes a fluid passage through which a cooling or heating medium circulates.
 7. The polishing apparatus according to claim 6, further comprising a temperature controller for adjusting and controlling a temperature of the cooling or heating medium circulating said fluid passage.
 8. A polishing apparatus, comprising: a polishing table having a polishing surface; a dresser for dressing said polishing surface; a substrate holder for holding and pressing a substrate against said polishing surface to polish the substrate with relative movement between said polishing surface and the substrate, wherein said dresser includes a circular holding member for holding a circular dummy substrate, and a dressing member arranged around said circular holding member.
 9. The polishing apparatus according to claim 8, wherein: said circular holding member and said dressing member have rotating shafts, respectively; and said rotating shafts are concentrically arranged and are rotatable independently of each other.
 10. The polishing apparatus according to claim 8, wherein said circular holding member includes therein a fluid passage through which a cooling or heating medium circulates.
 11. The polishing apparatus according to claim 10, wherein said circular holding member is operable to press the dummy substrate against said polishing surface of said polishing table during polishing of the substrate.
 12. The polishing apparatus according to claim 11, wherein: said polishing surface of said polishing table comprises a surface of a polishing pad attached to an upper surface of said polishing table; and said polishing apparatus is operable such that, after said polishing pad is replaced with a new polishing pad, said dummy substrate held by said circular holding member and said dressing member are pressed against a polishing surface of said new polishing pad to thereby break in said polishing surface of said new polishing pad.
 13. The polishing apparatus according to claim 8, wherein a SiC wafer is used as the dummy substrate.
 14. The polishing apparatus according to claim 8, wherein said circular holding member is operable to press the dummy substrate against said polishing surface of said polishing table during polishing of the substrate. 